Efficiency of three wind energy generator systems

Artikel i vetenskaplig tidskrift, 1996

This paper presents a method to calculate
the average efficiency from the turbine shaft to the
grid in wind energy converters. The average
efficiency of three 500 kW systems are compared. The
systems are: a conventional grid-connected four-pole
induction generator equipped with a gear, a variablespeed
synchronous generator equipped with a gear and
a frequency converter, and a directly driven variablespeed
generator equipped with a frequency converter.
In this paper it is shown that a variable-speed
generator system can be almost as efficient as one for
constant speed, although it has much higher losses at
rated load. The increased turbine efficiency that
variable speed leads to has not been included in this
paper. It is also found that a directly driven generator
can be more efficient than a conventional four-pole
generator equipped with a gear.